Straddle
Buy a call and a put at the same strike, same expiry.
Payoff is a V. You profit if the underlying moves far enough in either direction to cover the combined premium. Direction-neutral, long vega, long gamma, short theta.
This is the cleanest expression of "I think it will move but I do not know which way" - typically used around earnings or binary events.
The catch: everyone else knows the event is coming, so implied vol is already elevated. Buying a straddle into a known event often loses even when the move happens, because vol collapses afterwards. That "vol crush" question is a common interview follow-up.
Strangle
Buy an out-of-the-money call and an out-of-the-money put at different strikes.
Cheaper than a straddle because both legs start out of the money, but it needs a larger move to pay. Payoff is a flat-bottomed V.
Vertical spread
Buy one option and sell another of the same type at a different strike.
A call spread (buy lower strike, sell higher) is a bounded bullish bet: cheaper than the outright call, with profit capped at the strike difference. Both risk and reward are limited.
Spreads are much less sensitive to volatility than outright options, because the long and short vega largely offset. If you have a directional view but no volatility view, a spread expresses it more purely.
Butterfly
Buy one low strike, sell two middle, buy one high. A bet that the underlying stays near the middle strike. Cheap, with limited profit, and effectively a bet that realised volatility will be low.
The interview technique
Draw the payoff diagram. Almost every question about these structures - maximum loss, breakeven, what happens if it expires here - is immediate from the picture and error-prone without it.
Then state the Greeks qualitatively: is it long or short vega, gamma, theta? That combination answers "what view does this express?" reliably.
Practise in finance and derivatives.